You can accomplish the same thing by using a local password which is the same for all of your PCs, along with the same user name. I've been doing that, without a Workgroup, since that days of XP and have never had a problem seeing files, or printers and across mixed OS versions. You will have to decide to allow or not allow sharing on a folder by folder basis (this is inherited so its not that big a deal).
I am slightly confused by it all but I *think* once you've allowed microsoft's online account to control your PC you are slightly screwed and can't revert.
Part of the problem I had was that because I hadn't put any password in, Windows was booting straight in with zero security even though I had asked for it(!). And weirdly I wasn't given the opportunity to set one up at the time when one logs in...
You can create another account that does not have anything to do with your Microsoft account at anytime, and use this to run the PC as administrator
Just start to add another user, click on the I do not have user login details, then select create an account without Microsoft account and follow the prompts - You will have to log into any Modern Apps you use individually but otherwise will work as you would expect.
It's best to keep the Microsoft account active and having your account linked to your system allows more leeway for licensing if you change major hardware
Add User Account in Windows 10 - Windows 10 User Accounts Tutorials
In this case you are using the default Workgroup, called "Workgroup" although you are using it in a rather limited way
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